Such devices for longitudinally guiding a motor vehicle are also known as ACC (adaptive cruise control) systems and typically have a radar sensor as a sensor system which can be used to measure the distances and relative speeds of preceding vehicles. This method makes it possible to follow a vehicle traveling directly ahead, the so-called target object, at a suitable distance or, more precisely, in a suitably selected time interval. In free driving mode when no target object is present, the speed is regulated to a setpoint speed, which in the systems in use today is specified by a desired speed selected by the driver.
In specific conditions, for example when driving in tight curves, it is possible that the regulation may not be adapted to the current situation so that the curve is taken at an excessively high speed. The driver is then forced to intervene in the longitudinal guidance and temporarily deactivate the ACC system.
In German Patent Application Nos. DE 198 21 803 and DE 199 31 161, longitudinal guidance systems are described having a connection to a navigation system which is also present in the vehicle so that the route information supplied by the navigation system, in particular the information readable from a digital map concerning the curvature of the section of roadway directly ahead, can be included in the speed regulation.